Telephone system



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Dec. 10, 1940 R. RAYMOND 2.2241596 TELEPHONE SYSTEM Filed May 15, 1939 15 Sheets-Sheet 8 5 If 0 2 um Q 5 u, u m o m INVENTOR RRAVMOND ATTORNEY 1940? R. RAYMOND 2224,696 TELEPHONE SYSTEM Filed May 13, 1939 13 Sheets-Sheet 9- NUMBER SENDER //v l EN TOR R. RA VMOND ATTORNEY IN VE N TOR R. RA rue/v0 A 7' TORNE V D 1940- R. RAYMOND TELEPHONE SYSTEM Filed May 15, 1959 13 Sheets-Sheet 1o Dec. 10, 1940. R. RAYMOND TELEPHONE SYSTEM Filed May 13, 1939 15 Sheets-Sheet l3 INVENTOR R RAYMOND IH I' H III-II ESE mmmzbz A TTOPNE Y Patented Dec. 10, 1940 PATENT OFFICE TELEPHONE SYSTEM Ralph Raymond, Nyack, N.-Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application May 13, 1939, Serial No. 273,387

13 Claims. (Cl. 179-27) This invention relates to telephone systems and more particularly to line number indicating devices used in such systems.

In telephone systems employing line extending switches for completing a part of a telephone connection, it becomes necessary on certain types of calls, such as a toll call, to supply the operating company with information as to the identity of the calling line number. Under such circumstances the line extending switches controlled by the calling subscriber serve to connect the line to an operators position where facilities are provided to fin'ther extend the connection to the wanted station after the operator has been apprised by the calling subscriber of the identity of said station. This information is necessary to permit the operating company to bill the calling station for the cost of the toll call. Facilities are usually provided for verifying or checking? the line number, as given by the calling subscriber, so that the operating company will make no error in properly charging the toll call to the station from which the call is made.

At the present time, number checking is accomplished in divers ways among which is the well-known checking multiple method whereby the operator, upon being apprised of the calling line number, applies the tip conductor of a checking cord to the sleeve conductor of the calling line in the checking multiple; the method whereby the operator, after having beengiven the number by the subscriber, sets a train of switching selectors to select the terminal of the line number as given by the calling subscriber and thereafter impresses a tone over the sleeve conductor of the extended connection that is picked up again over the sleeve of the switch train if the number as given by the subscriber over the extended connection coincides with the line terminal reached by the switch train; and other methods whereby a lamp display is given of the calling line number, the lamp display circuit being set by trains of impulses characteristic of the calling line. b

These and other means have been used with varying degrees of success. The difiiculty is, however, that all these methods and means either require the operator to obtain the line number from the calling subscriber, thereby slowing down the service, or else involve a comparatively large amount of equipment of a character costly to maintain.

The object of the present invention is to provide a more direct and efficient method for determining the calling subscriber's line number,

which depends upon a circuit structure and related apparatus which are both reliable in operation and economical to maintain.

' The apparatus and organization of circuits described in the present invention comprise means 5 for number checking which are based upon the use of a positive hunting circuit for locating a conductor individual to the calling line and in response to which a sequence of circuit operations is started that results in the display of the 10 corresponding line number on an indicating device'before the operator. In accordance with the invention, therefore, one specific embodiment of which is disclosed herein by way of illustration, this is accomplished in the following im- 15 proved manner:

There is provided a number finder circuit for each central oiiice unit of ten thousand subscriber numbers, and if two or more such units make common use of the same outgoin'g trunk groups 20 to long distance or special service operators, their several number finders may be preferentially arranged to operate one at a time over common. equipment in the manner hereinafter set forth. The number finder is adapted to record the num- 25 her of the calling line by locating a discriminating tone applied to the sleeve conductor thereof at the operators position to which the calling line has been extended, after which, over a suitable connector channel, the line record is trans- 3 ferred to a number sender of which a number may be provided depending upon the needs of the trailic. Inasmuch as the long distance operators position may be located in a different oflice from that in which the call originates, the 35 number finder is adapted to record and the number sender is adapted to receive a calling ofilce designation as well as the calling subscribers numerical designation. Thus, where a plurality of number finders are provided, one for 40 each omce unit, each of them identifies the name or number of the oflice with which it is associated, and this identification is then transmitted into the sender which may be common to a plurality of such finders. The number finder is fur- 5 ther adapted to record and transmit into the. sender the line numberof an individual or private branch exchange line, the registration number oi. a two-party message rate line with a special indication when it is the tip station calling, and 50 some one of the station numbers of a fiat rate' party line, with a special indication that it is a fiat rate party line.

A clearer conception of the scope and purpose of the invention may be obtained from a consid- 55 eration of the following description and attached drawings Figs. 1 to 13, inclusive, which, when arranged as shown in Fig. 1A, disclose all the essential elements of a typical telephone system with which the invention may be adapted to operate, and in which:

Fig. 1 shows a special service trunk accessible to the calling lines of a typical telephone sytem via the usual switching selectors;

Fig. 2 shows two service cords with which calls over the service trunk may be accepted, and a positional call indicator steering circuit;

Figs. 7 and 8 show the positional call indicator register and display circuit which cooperates with said steering circuit;

Fig. 3 shows an operator's. recording bompleting trunk accessible to special service operators;

Fig. 4 shows a long distance operator's cord and a schematic showing of a call indicator located at the long distance position, the former being used to accept calls incoming over the rewhat are ordinarily known as district selectors on frame D5 which have accessibility to terminal sets of a plurality of terminal banks to which are connected trunk groups that extend in various outward directions for completing calls thereover to wanted destinations. In cases where the quantity of traffic is limited in certain directions and the trunks for such service are relatively few in number, they are not terminated on the banks of the district selector frame DS but on those of an ofiice selector frame OS, accessibility to which is then obtained by guiding the district selector I I 9 to the terminals of the wanted group of ofilce selectors from which an idle one is selected, such as I20 for instance, to hunt over and choose an idle trunk in the wanted direction. In Fig. 1 it is assumed that the trunks to an operator's position, say the special operators position, terminate on the ofllce frame OS, and that the subscriber A in reaching such a position dials a specified code assigned to long distance service, which code is adapted, through recording and controlling equipment, to guide the district selector I I9 paired with a chosen line finder III to the terminals of an ofilce selector I20 that will be selectively moved into position to cause its brushes to engage the terminals of an idle position trunk I2 I. I

Inasmuch as the setting of the selectors and the controlling equipment therefor to reach a special service trunk form no part of this invention, 'the description of the various apparatus structures and the connecting circuits to operate them have been omitted, reference being made to Patent 1,862,549 issued to R. Raymond et al. on June 14, 1932, which discloses and describes the automatic extension of a calling line over line finders, district and ofllce selectors of a. wellknown panel type equipment of the kind used in the present invention to illustrate one of its specific embodiments. It is understood, however, that while the invention is herein disclosed for being obvious to any one skilled'in the art of telephony that the invention may be easily adapted, with slight or no modification, to any other type of telephone equipment used for extending calling lines without in the slightest departing from its scope or functions.

In the following description of the operation of the invention it will be assumed then that the subscriber A has dialed a special service trunk and that, as a result, the train of switching selectors-comprising line finder II8, district, selector H9 and office selector I20 have been operated to extend a connection from the line finder terminals of the calling line A to the ofiice frame terminals of the special service trunk I2I, and that, in the manner described in the abovementioned patent, the line relay I24 of the district selector H9 and relay I24 of the office selector I20 are operated to hold their respective selectors in the position indicated in the figure.

The extension of the calling line to the special service trunk I2I results in the operation of relay I00 therein over a circuit extending from battery through the winding of relay I00, N0. 1 back contacts of relay I05, over the tip side of the extended connection, station loop, ring side of said connection, to ground on the No. 3 back contacts of relay I05. Relay I00 operates and closes an obvious circuit for relay IOI which, on operating, closes an obvious circuit for relay I01 over its No. 3 contacts, connects ground over its No.1 contacts and over the No. 1 contacts of relay l00 to conductor I25 to start the link (Figs. 5'

and 6), connects battery over its No. 2 contacts in partial preparation of the circuit of the "calling line lamp I04 and disconnects ground over its individual test conductor II5 to the links so that the trunk finder of the link will stop on the selected service trunk as hereinafter set forth. Relay I01, in operating, grounds the selector sleeve conductor III through retardation coll I06 to holdlocked relays I24 and I24 of the office and district selectors, respectively, and thereby hold these selectors in an operated position, and further connects holding ground to conductor I30.

The ground on conductor I25 completes a signal to an idle link circuit to start hunting for the callingtrunk. The ground on said conductor, therefore, completes a circuit over the upper contacts of relay 501, No. 2 contacts of relay 508, conductor 509, right springs of cam 603 of the first idle link in the group, conductor 60l, winding of relay 5l2 to battery. Relay 5I2 operates, looks over its No. 4 front contacts to ground on the left upper springs of cam IiI5 via conductor 5I0, commutator segment 5I5, brushes 5H and 5I9, commutator segment 5I0 of the trunk finder, conductor 520, right lower spring of" cam BIG, to ground on the left upper spring of cam 6I5, closes an obvious circuit over its No. 3 contacts and conductor 52l for relay 026 which operates and then locks over its upper winding and No. 3 contacts 'and lower right spring of cam 023 to the above traced ground on cam IiI5. Relay 626 then closes a circuit for relay 508 extending from battery over the upper outer contacts of relay 522, upper winding of relay 500, No. 1 front contacts of relay 5I2, conductor 523, No. 4 contacts of relay 625, left upper spring of cam BIG to ground on cam SIS. This relay locks to ground over its No. 4 contacts, back contacts of relay 525 and the contacts of key 525. The operation of relay 512 closes a circuit for the up-drive magnet 513 of the trunk finder ex- 5 tending from battery through the winding of said magnet, No. 2 contacts of relay 512, conductor 524, right lower spring of cam 523 to the aforetraced ground on cam 515. This magnet now controls the upward movement of the selector l0 elevator in the known manner and causes the brushes 551 to 505, inclusive, to engage the corresponding bank terminals to which are extended the trunk conductors and among which is to be found the seized trunk to the operator's position which is characterized by the absence of ground inclusive, likewise move upwardly, engaging the segments of the commutator in the known manner. In the interval that the brushes 501 to 505 are between bank terminals, relay 512 remains locked to the aforetraced ground on cam 515 over an unlnsulated portion of commutator 515, whereas when the brushes are enga ing a set of terminals and brush 511 engages an insulating segment, relay 512 will be held operated to ground on conductor 115 of an idle trunk, which ground traces to the winding of relay 512 over the following path: brush 504, upper outer back contacts of relay 521,

No. 4 contacts of relay 512 to the winding thereof.

Hence the brush elevator will continue its upward drive until the wanted set of terminals is reached, at which time the absence of locking ground on conductor 115 for relay 512 will cause this relay to unlock which, upon releasing, re-

leases in turn up-drivemagnet 513, thereby-causing the brush elevator to stop on the selected set of terminals The release of relay 512 opens the operating 4o circuit of relay 508 and that of relay 525, both of which are locked, and further connects the aforetraced ground on cam 515 over its No; 4 contacts to the test terminal of the trunk via brush 504 to prevent another hunting link from stopping on the terminals of the selected trunk, and completes a circuit for sequence switch magnet 500 extending from battery through the winding of said magnet, conductor 531, No. 1 back contacts of relay 512, conductor 523, No. 4 contacts of re-- lay 626, left upper spring of cam 515 to the aforetraced ground on cam 515. Magnet 500 operates and advances the switch into position 2 or 11 depending upon whether the switch is originally in normal position 1 or normal position 10.

In position 2 or 11 a series path is closed through the left upper and right lower springs of cm 505, top normal springs of jack 530, the first link in the chain after the one taken into use which is in the "awaiting allotmen position 18 or 9, left lower and right upper springs of cam 530' in said link corresponding to cam 530, thence to the winding of a relay corresponding to relay 525 of the link in the awaiting allotment position.

This relay locks and closes a circuit for magnet 500 of said link which extends from ground on cam 515 of said link, left upper spring of cam 615 of said link, No. 4 contacts of relay 525, conductor 523, No. 1 back contacts of relay 512 of said link, conductor 531, winding of magnet 500 to battery. Magnet 500 operates vious circuit for relay 502 which operates and connects ground to resistance 528 connected through resistance 523 to battery, and the combined network is now completed over a path extending through the winding of relay 525, conductor 530, upper springs of cam 503, bottom contacts of relay 523, left lower and right upper, springs of cam 501, conductor 531, brush 505 and the terminal engaged thereby, conductor 113, No.

1 back contacts of relay 110, winding of relay 108 10 to battery. Relay operates in this circuit which, over its No. 3 contacts, locks to ground on conductor and connects ground to conductor 113 the effect of which is to operate relay 525. Relay 108, in operating, also removes ground 15 from conductor 125.

Relay 525, in operating, unlocks relay 508 thereby preparing the start circuit to handle the next call and also completes a circuit for relay 532 which extends from ground on the upper 20 contacts of key 525, front contacts of relay 525, conductor 533, right upper and left lower springs of cam 502, conductor 533, winding of relay 532, conductor 534, resistance 532 to battery. Relay 532 operates, locks over its No. 4 contacts to 25 ground on the upper springs of cam 515, connects the same ground to the upper winding of relay 529 via conductor 535, No. 1 contacts of relay 525, causing said relay 129 to operate, to release relay 525 and to perform functions noted hereinafter, 30 and completes a circuit for magnet 500 which extends from ground on cam 515, left upper spring of cam 511, conductor 534, No. 6 contacts of relay 532, conductor 535, upper springs of cam 505, winding of magnet 500 to battery. Magnet 500 85 operates and advances the sequence switch to position 3 whereupon relay 532 releases.

Relay 528 operates as the switch passes through position 2 or 11 over a circuit extending from battery through its lower winding, lower 40 springs of cam 518, top back contacts of relay 521, left upper spring of cam 511 to ground on cam ,515. It, however, performs no function at this time. Moreover, since relay 521 is normal,

a path is provided for advancing the switch into 45 position 4 or 13, the circuit being from ground once of resistance battery on the terminal which 75 of cam 622, while the operation of relay 528 .before relay 521 grounds the middle winding of relay 521 and the operation of relay 525 serves to connect the lower winding to the middle and upper windings via battery through the lower winding, No. 2 contacts of relay 525 to the ungrounded side of the middle winding.

It is further evident that while relay 529 holds up over its original operating circuit through the back contact of relay 521 it also has a supplementary locking path from ground on commutator strip 550 over commutator brushes 559 and 551, commutator strip 539, conductor 5, lower springs of cam 524, top inner contacts of said relay. Since the commutator strip is designed to present a conducting strip to the terminal engaging brush while the brush is between terminals and an insulating strip when said terminal brush engages a terminal of a terminal set in the bank 550, it is clear that when an idle sender is encountered and, as a result, relay 521 operates in a circuit presently to be described, relay 529 releases, in turn opening the circuit of the updrive magnet 555 and thereby causes the selector elevator to come to rest with the terminal brush set engaged with the terminals of an idle sender.

Idle number senders are characterized by battery through 270 ohms resistance and, assuming that the sender shown in Fig. 9 is the first idle one encountered, a circuit will be closed from battery through resistance 92I, No. 1 contacts of relay 905, conductor 903, brush 553 through the upper and lower windings of relay 521 as previously traced, to ground on the upper inner contacts of relay 528. Relay 521 operates in this circuit, short-circuits its middle winding with ground on the No. 5 contacts of relay 525 via its own top front contacts, and closes a locking circuit through its lower winding to the aforetraced ground. This circuit so alters the potential or. brush 553 that no other link circuit which may be hunting can stop on the seized number sender. The operation of relay 521. opens the circuit of relay 529, in turn stopping the selector from hunting as before described.

When relay 521 operates, it opens the operating path of relay 528 which, upon releasing, advances the sequence switch to position 5 or 14 over a circuit path extending from the aforetraced ground on conductor 534, No. 5 and No. 6 contacts of relay 532, bottom front contacts of relay 621, top back contacts of relay 528, left lower spring of cam 5I3, positioning cam 535, winding of magnet 500 to battery. Relay 520 is made slow in releasing so that if another link should be hunting over the same sender terminals is fully operated, relay 521 will release, the brush elevator will move off the terminal, the link will continue hunting, relay 528 will remain operated and the switch will not be advanced out of the hunting position.

If the selector brush elevator travels to the top of the bank without finding an idle number sender, relay 532 will operate in a circuit extending from battery through resistance 532, conductor 534, winding of relay 532, conductor 533, upper springs of cam "525, conductor 542, commutator segment 555, brush 51, brush 59 to ground on commutator segment 50. Relay 532 looks to a previously traced circuit, opens the circuit of the up-drive magnet 555, thereby stopping the upward movement of the selector, opens the test -5 circuit to test brush 553, and closes the circuit of the down-drive magnet 551 over a circuit path which extends from battery through the winding of said magnet, conductor 543, lower springs of cam 520, conductor 535, No. 6 contacts of relay 532, to the aforetraced groundon conductor 534. The selector is driven back to its normal position in which brush 558 engages commutator segment 545 to short-circuit relay 532 by extending ground to resistance 532 via the right springs of cam 52L The release of relay 532 releases the down-drive magnet 551, operates the up-drive magnet 555 as before, closes once again the test circuit to brush 553 and the link starts to hunt as before.

The seizure of the sender will caues the removal of ground from conductor 903 in the manner hereinafter set forth whereupon relay 521 will release, which closes a circuit from battery through the winding of sequence switch magnet 500, lower right spring of cam 6I3, top back contact of relay 521, left upper spring on cam 6" to ground on cam 5I5. Sequence switch 500 is advanced to position 6 in this circuit. In position 5 the sender and the special service trunk I2I are connected together by the trunk and sender selector brushes over paths that will be detailed henceforth in connection with circuits to be traced thereover.

As already stated, the link seizes the first number sender whose conductor 903 is connected to resistance battery 92I through the No. 1 contacts of relay 905. The link, in position 6, cuts through conductors 90I, 902, 904 and 905 from the sender to the trunk, whereupon a series circuit is completed between relay I09 in the trunk, relay 628 in the link and the low winding of relay 9 I in the sender. This circuit traces from battery through the winding of relay I09, No. 2 back contacts of relay I05, conductor II5, brush 503, left contacts of cam upper winding of relay 528, brush 552, conductor 904, No. 1 back contacts of relay 901, No. 1 contacts of relay 9I5, upper low resistance winding of relay 9l0 to ground. The current flowing in this circuit is sufficient to operate relays I09 and 9I0 but not relay 528, whereupon relay I I0 in the trunk operates over an obvious circuit completed over the front contacts of relay I09, and relay 909 in the sender operates over an obvious circuit completed over the contacts of relay 9I0,'relay 908 then operating over an obvious circuit completed from the front contacts of relay 909 and looking to ground over its No. 3 contacts. Relay 908, in operating, closes an obvious circuit to the winding of relay 905 which operates to perform functions hereinafter noted. Relay H0 in the trunk, upon operating, locks over its No. 2 contacts to ground on conductor I30.

In the meanwhile ground is removed from conductor H3 in the link and, due to the operation of relay IIO, this conductor is switched from the winding of relay I00 which is locked, to the lower winding of relay I02 via the No. 2 back contacts of relay I03.

Following the operation of relay 905 in the sender, a circuit is completed for relay I200 in the connector extending from battery on the No. 2 contacts of relay 905, No. 1 contacts of relay 9, conductor 922, winding of relay I200, to ground. As shown in Fig. 12, relay I200 is the 75 first of a group of relays I200 to I200" each of which is individual to a sender. These relays are disposed in a preference lock-out circuit arthe group can er will, of course, operate but nothing occurs in consequence thereof because of the operatedv condition of the-relay I 200' ahead of relay I 200 which breaks the upper ground chain to operate relay I202 as subsequently set forth. When relay I200 releases (assuming that it is operated when relay I200 operates), a circuit is completed for multicontact I202 extending from ground on the contacts of relay II, No. 1 back contacts of each of the relays I200, etc., No. 1 front contacts of the operated relay I200, winding of relay I202 to battery. Relay I202 operates'and locks over its No. 3 contacts, conductor I203, No. 4 normal contacts of relay 9 to ground on conductor 900.

Thus as a result of the extension of the calling line to a special service trunk terminating at the operators position, an idle number sender has been connected to the trunk via the link and to the connector channel, the other side of which will be connected to a number finder disclosed in Figs. 12 and 13 in the manner to be described shortly. As a result of these connections the sender wil transmit a tone signal over the sleeve conductor of the connection which the number finder will proceed to identify. Relay I 202, on operating, connects the secondary of tone source I204 of two frequencies fl and f2 through the No. 1 contacts of relay I202, conductor 905, brush 55I, upper springs of cam 620, top inner contacts of relay 521, brush 50I, conductor I I1, sleeve conductor of the extended connection, bottom contacts of relay I23, low-pass filter I28, upper contactsof relay I23, condenser I21, linefinder brush and terminal of the calling line, conductor II2, condenser I300 and thence to the spring of cam I 303 in the sequence switch of the number finder of the ofiice unit to which the calling line belongs. If relay I23 of the district selector is operated as a signal that the tip party of a two-party message rate line is calling, the low-pass filter I 28 is removed from the line and both frequencies fl and f2 will pass to conductor H2 of the number finder. Otherwise the lowpass filter will be in circuit and one frequency only is transmitted, the other being shunted to ground. Relay I202, on operating, further closes an obvious circuit over its No. 2 contacts and conductor I206 to the winding of relay I001 which operates to perform functions noted hereinafter.

-Relay I202 closes one set of channel contacts between the register relays of the sender and the recording equipment of the finder which began functioning to record the calling line number when tone was transmitted thereto over the sleeve of the connection.

In the organization of the number finder, shown in Fig. 13 and in the left portion of Fig. 12, each block of one thousand consecutiv l ne through its winding (as round would be con-' preference have its own relay I200 operated, relay I 200 of the first se'ndnumbers is assigned to ten sequence switches. in-

elusive, of known construction and to a set of party line multicontact relay sequence switch for each one there being one hundred consecutive number subdivision of the one thousand numbers.

Thus considering Fig. 13, there are To each group of ten switches is assigned a thousands multicontact relay indicated by the group of relays I2I0 to I2I9 in Fig. 12, and two additional relays which, in Fig. 13, are illustrated by relays I340 and I340 for the lowermost group of switches R00 to R99, and relays I349 and I349 for the uppermost group of switches R90 to R99, the-intermediate relays being omitted from the drawings. There is also provided a common group of ten hundreds relays I220 to I229, one for each hundred subdivision for the thousand block of lines which are arranged for operative cooperation with their respective hundreds switch in each of the ten groups of switches in the manner hereinafter set forth.

Each switch in each group is allocated to a particular one-hundred line subdivision of the entire one-thousand line group, the lowest switch preferably being assigned to the lowest subdivision and other switches, ascendingly, to the other and higher subdivisions. Each switch is provided with thirty-one cams of which cams I303 to I321, inclusive. for example, are collared together according to the known method and the springs thereof are each connected to a conductor, like conductor I I2, for instance, extending to the winding of the cut-off relay of the subscribers line in the one-hundred subdivision assigned to the particular switch.

The disposition of the line sleeve conductors in the various springs of the cams I303 to I321, inclusive, is made according to the hundreds, tens and units designations of each individual line represented by a sleeve conductor, and the face of the cam engaging each particular spring is cut correspondingly to produce, as the switch is rotated through one revolution as hereinafter described, a group of pulses which designates the number of the line.

Each of the springs which represents a fiat rate party line as, for instance, the line repre sented by conductor I334, is also extended to a contact in one of the two relays associated with the same thousand line numbers as, for instance, relay I349 of the uppermost group of switches R90 to R99.

Mention has already been made of the fact that when the sender becomes attached to the special service trunk and to the connector channel, a tone of two frequencies is applied back over the sleeve conductor of the extended connection, and that this conductor further extends to a spring of a sequence switch in the number finder in the block of ten switches assigned to the thousand numbers containing the calling number, and particularly to the switch con-taining the hundreds subdivision thereof which includes the hundreds digit of the calling number. In the description and for purposes of illustration, the sleeve was traced through to conductor H2 which is the extension of the sleeve of the calling line A. Now let it be further assumed that the calling line A belongs in the last thousands group and in the last hundreds of the group, thereby having 9 for its thousands digit and 9 for its hundreds digit. This being the case, conductor I I2 is extended to a cam, say cam I303, in the switch R99, to which the tone circuit was last traced. And this switch is, of course, in the group of switches provided for lines 9000-9999, the last switch in the group, and is provided for the last group of one hundred lines.

At the time the tone is transmitted over the sleeve connection, the number finder is, of course, normal and, therefore, all of its switches are in position 1. Consequently, the tone circuit on conductor H2 is further extended over the right lower contact of cam I328, conductor I331, rectifier I201, lower winding of relay I2I9 to ground. Had the calling line belonged in any other hundreds subdivision of the thousand line block, then the conductor I I2 would have been extended to a spring in the appropriate one of the ten sequence switches assigned to this block, and the tone circuit would then have been extended over cam I320 of the appropriate switch, and thence to conductor I331 over which the previously described circuit is completed to the winding of relay I2I9.

If the calling line is located in any other thousand block, its sleeve conductor II2 would have been extended to the appropriate group of switches and to the one switch therein provided for the one-hundred line subdivision thereof. Since there is one group relay for every thousand lines (I2I0 to I2I9) with its energizing circuit completed to every one of the switches in the thousand block, the operated relay in the group of relays I2I0 to I2I9 will mark the thousands designation of the calling line number.

For the purpose of illustrating the operation of the invention as a whole, let us assume that the calling line number is 0963. This means that the sleeve conductor II2 of the line is extended to the last swi ch R99 in the uppermost block of switches R90 to R99, and is connected to a spring I303 in this switch. According to the operations already described, the presence of tone on this conductor causes the operation of the thousands group relay I2 I 9.

Relay I2I9, upon operating, connects ground from the No. 1 back contact of relay I2I0 serially through the No. 1 back contacts of intermediate relays I2II to I2I8, No. 1 front contact of relay I2I9, conductor I208, right upper contact of cam I30I, cam I300, winding of switch magnet R99 to battery. Similar parallel circuits are established over the other nine cams corresponding in cam I30I to each of the other nine switch magnets R90 to R98, so that the entire block of ten switches advances out of position 1 and into position 2. Relay I2I9 further closes a locking circuit over its upper winding and No. 10 contacts to ground on oil-normal conductor I330, which ground, however, is not effective until the ninth block of switches has advanced to position 2, at

which time ground is connected to conductor I338 by the cams I302; it further closes an obvious circuit for multi-contact relay I230 which operates; and further grounds a group of conductors to designate the ofiice code and thousands digit of the calling line in the manner to be shortly described.

Relay I230, upon operating, closes an obvious circuit for relay I20I which removes operating ground for the sender connector relays I202, conand SIS records the nects ground to conductor I235 which initiates the operation of any suitable timing circuit I356 that counts off a predetermined time for the number finding and sending operations to take place, and closes the channel through between the number finder and number sender over channel leads 1 to 23, inclusive.

It has already been stated that one finder circuit is assigned to each oflice unit of ten thousand lines. Since each of these units may be in a different building or in a different telephone area and may canalize all long distance calls into one common long distance center, it will be necessary for the recording operator to ascertain the particular ofiice in which the calling line is located. For this purpose the circuits are arranged to provide an oflice indication, in addition to the indication of the called line member, with each finder identifying its own ofiice unit by the permanent connection of ground to one or more of four conductors I23I, I232, I234 and I235 extending over channel leads 1 to 4, inclusive, to relays 9 I 6 to 9I9, inclusive, of the number sender, over the respective conductors 923 to 026, inclusive. The particular relay or the combination of relays operated by the grounded conductors determines, of course, the identity of the calling ofiice. Thus, with the four relays BIG, 9", 9I8 and BIS, nine separate oflice code indications may be obtained as follows:

Relays operated Fig. 9

916 (office 1) If the number of ofllce units having access to the common special service or toll center is greater than nine, the number of identifications may be increased by adding as many relays as required and by adding between these relays and the thousands relay I2I0 as many additional conductors over the connector channel as may be required. For the purpose of illustration, however, it will be assumed that the number of ofiice units does not exceed nine and that the identification of the unit associated with the finder of Figs. 12 and 13 is established by the connection of ground to conductors I234 and I235. Therefore, when relay I2I9 operates and the connecting channel between the finder and sender is closed through, a circuit is completed which extends from ground on the No. 4 contacts of relay I2I9, conductor I234, No. 3 contacts of relay I230, conductor 025, winding of relay I8, to battery. Relay 9I0 operates and locks over its No. 2 contacts to ground on conductor 000. Another circuit is completed which extends from ground on the No. contacts of relay I2I9, conductor I235, No. 4 contacts of the connector channel, conductor 926, winding of relay SIS to battery. Relay SIS operates and looks over its No. 2 contacts to ground on conductor 900. The operation of relays 9l0 identification of the calling oflice according to the above code.

Relay I2I9 further grounds one or more of the four conductors I24I, I242, I244 and I245 which are multipled to the other nine thousands relays in an appropriate combination for each thousands digit, to operate one or more of the four correto position 3, a circuit is completed. from conducsponding relays M, H02, H04 and H05 in the tor II2 over said cam, conductor I339,-rectifier number sender to record therein the thousands I259, lower winding of relay I229 to ground, cau s designation of the calling subscriber's number. ing this relay to operate and then lock over its 5 Since there are but ten designations in this case, upper winding and No. 15 contacts to ground on the identification of each of the ten one-thousand conductor I338. Relay I229, in operating, groups i as follows; grounds aselection of four conductors, I 26I, I262,

Thousand group Conductors ounded Relays perated equence switch magnets.

and continuing to advance into position 14 under aim-89991 .13: iiii iii qasi ii iii -ms h n l of ams I300.

12 -1 11041105 It has been assumed that the subscriber's hundreds designation is 9 and that, for this reason,

It has been assumed that the calling line is in the sleeve conductor relating thereto was ex- 20 the 90009999 block. Since, for the identificatended to a spring associated with a cam on the tion of this block of lines, it becomes necessary to switch R99 which, in turn, resulted in the operaoperate relays H04 and H05 in the sender, the tion and locking of relay I229. The recording operation of relay I2I9 causes ground to be conof the hundreds digit 9 is carried out on the same nected to conductors I244 and I245 and the folbasis as the thousands registration. That is to 25 lowing two circuits are thereby completed (1) say, four relays IIII, III2, I H4 and III5 are ground on the No. 7 contacts of relay I2I9, conprovided which are operated singly or in comductor I244, No. 6 contacts of the connector chanbination for each one of the digits except 0 over nel, conductor I I06, winding of relay II04 to batconductors extending to separate sets of contacts 90 tery, causing this relay to operate and lock over on each of the ten relays I220 to H29. The its No. 1 contacts to ground on conductor 900; order of the combinations is the same as for the conductor I245, No. 5 contacts of the connector hundreds digit 9, it becomes necessary to operchannel, conductor II03, winding of relay H05 to ate relays III4 and I I I5. The circuits for these battery, causing said relay to operate and lock two relays are as follows: one circuit may be 35 over its No. 1 contacts to ground on conductor traced from ground onthe No. 3 contacts of re- 900. lay I229, conductor I264, No. 10 channel lead,

her finder following the operation of relay I2I9 The other circuit may be traced from ground on in response to the appearance of the tone current No. 2 contacts of relay I223, conductor I265, No. 40 impressed on the sleeve extension II2 of the call- 9 channel lead, conductor III6, winding of reing line A located in the 9000 to 9999 block of lay III 5 to battery. Both of these relays operlines, the thousands relay grounds a selection of ate to record the digit 9 and look over their reone or more of four conductors I23I, I232, I234 spective No. 1 contacts to ground on conducand I 235 to register the code of the calling oiiice tor 900. 45 by the operation of one or more relays 9I6, 9II, In passing through positions 4 to 11. the tone 9! and 9I9; it grounds a selection of one or more path from the sleeve extension I I2 of the callof four conductors I24I, I242, I244 and I245 to lug line is carried through the left register the code of the thousands digit by the 'tacts of cam I328, conductor I34I, rectifier I209,

operation of one or more of the relays I IN, II02, No. 9 contacts of operated thousands relav I2I9l I I04 and H05 except for the digit 0 in which. no No. 5 contacts of the operated hundreds relay relays are operated in registration of the digit. a I229. conductor I233, to the left low circuit is closed to the block of switch magnets to cam of I329. From this point, the path is exadvance their respective sequence switches into ended over each of the ei ht separ position 3, and a locking circuit is provided for the bered positions on cams I330 and I33I to produce 55 thousands relay through positions 2 to 17, ina group of from 0 to 3 pulses in positions 4 to 7, elusive. inclusive. of the switch over conductors I342 to In position 3 of the switches R90 to R99, the I 345. inclusive. to operate the appropriate comtone conductor H2 is switched from the right bination of the four relays II2I, H22, H24 and 5 lower to the left lower spring of cam I328 where- "25 for recording the tens digit of the line numupon it is efi'ective to complete a circuit to operhe and t produce ano designation. Since the sleeve conductor of the a the a propriate combination of relays IIRI,

subscriber's line is disposed on one of the ten II 2 H34 and H35 for recording the units digit 65 switches R90 to R99 in accordance with the line 0f the line number. hundreds designation, it is obvious that the relay I w ll be observed that each s ring connec d operated will identify the hundreds digit of that to a sl eve conductor engages the face of an asnumber. Thus, if the subscribers hundreds sociated cam which is cut in certain difierent porelay I229 isconnected to the left lower spring of of the line indicated by the sleeve conductor. cam I328 of this switch, then, when this switch, Since the registration of the tens and units digalong with the other nine of the group, advances its in the sender is, like that of the thousands 26 

